The present invention relates generally to inflatable cushions used in vehicle occupant restraint systems. More particularly, this invention relates to a cushion constructed from fabric in the form of two congruent twelve-sided panels that may or may not share a common side. During the construction process, the panels are superimposed in congruent fashion and joined along their respective coincident edge portions to form a twelve-sided polygonal-shaped cushion.
An inflatable restraint cushion, or air bag, plays an important role in protecting the occupants of a vehicle from injury due to collision against the car body. Typically, the air bag is disposed within a supporting structure such as a steering wheel, dash panel, door panel, or other fixed portion of a car body in opposed or adjacent relationship to a seat in the vehicle. When inflated rapidly by the pressure of a reaction gas released from an inflator during a collision, the air bag serves as a protective barrier between the vehicle occupant and the steering wheel or other portion of the vehicle body against which the occupant might otherwise be thrown.
Air bags have been used in the past to protect both the vehicle operator and vehicle passengers. Systems for the protection of the vehicle operator are typically mounted in the steering column of the vehicle and utilize cushion constructions that deploy directly towards the driver. These driver-side air bags can be of a relatively simple configuration in that they function over a small, well-defined area between the driver and the steering column. Typically, driver-side air bags are circular or substantially circular in shape when viewed from the front or the back. Such circular air bags are frequently constructed by superimposing, aligning, and joining, along their respective coinciding edges, two generally circular fabric sections that are separately cut from a web or blank of air bag fabric.
It has been found that the amount of fabric used in the finished air bag contributes a large percentage of the costs of air bag production. While circular air bags are functionally effective, the circular shape of the front and back fabric panels from which the air bags are constructed does not lend itself to the efficient utilization of fabric during the manufacturing process. Specifically, the arrangement of these circular panels on a given blank of air bag fabric does not result in efficient fabric utilization or yield. Fabric is wasted in producing such circular cushions since the circular templates do not have straight edges which can be aligned with the edges of the fabric blank or which can be juxtaposed in close proximity on the fabric to provide common or nearly common adjacent edges with minimal fabric waste between neighboring cut sections. Furthermore, because use of circular or other curved panels frequently results in oddly-shaped sections of fabric between neighboring cut panels, utilizing such inter-panel fabric to make other necessary parts of the air bag (e.g., various reinforcements, tethers, doublers, etc.) is often difficult.
An additional problem with circular air bags is the amount of time consumed in the production operations of cutting, joining, and folding such bags. Straight edges, as are found in polygon-shaped panels, are easier to cut and to align for joining. The edges also provide a convenient means for folding the finished air bag into the appropriate shape for mounting into the steering column. The present invention addresses the problems of fabric utilization and production efficiency, in a manner not found in the prior art.
As used herein, it is intended that the following terms be defined as indicated: The term xe2x80x9cpolygonxe2x80x9d is a plane geometric figure having n sides and n vertices. The term xe2x80x9cdodecagonxe2x80x9d is a plane geometric figure having twelve sides and twelve vertices. A regular dodecagon is an equiangular polygon in which the twelve sides are of equal length. An xe2x80x9cAlternating Side Length (ASL) dodecagonxe2x80x9d is a symmetrical, twelve-sided polygon in which six sides have a first length and six sides have a second length, the second length being approximately twice as long as the first length, and the sides being arranged in an alternating sequence of short and long sides. A convex polygon is one for which no side, if extended, will enter the polygon. Unless otherwise specified, the term xe2x80x9cdodecagonxe2x80x9d shall refer to a convex, twelve-sided polygon. The term xe2x80x9ccongruentxe2x80x9d shall be used to mean capable of being superimposed so as to have a perimeter that is coincident throughout. The term xe2x80x9cfabricxe2x80x9d shall be used in a broad sense to describe any woven or non-woven fabric, film, polymer, combinations or composites thereof, or other suitable material from which the individual panels comprising an air bag may be constructed.
It is common, particularly in air bags designed for the protection of vehicle drivers, to find such air bags fabricated from the seaming or joining of two similarly-dimensioned circular panels along their respective perimeter edges after such circular panels have been cut from a blank of suitable air bag fabric and superimposed in congruent fashion. The instant invention provides for the use of relatively simple polygonal starting geometries for the fabric panels in order to reduce fabric waste by reducing the quantity of fabric between the panels on a fabric blank. Additionally, fabric waste may be reduced because, when such polygons are used, the inter-panel fabric (which might otherwise have to be discarded when circular panels are used) tends to have a straight-sided shape from which the fabrication of other components needed for air bag construction (e.g., reinforcements and the like) may be more easily constructed, thereby saving on the area of uncut fabric blank that must be used in the construction process.
It has been found that fabric utilization can be significantly improved by substituting polygon shapes, and particularly polygons having twelve sides, for the circular-shaped panels of the prior art. In one preferred embodiment, two such panels are individually cut and the cushion is constructed by superimposing the panels in congruent fashion (i.e., with coincident edges) and joining each of the twelve sides of one of the polygon-shaped panels to the respective coincident sides of the other panel. In another preferred embodiment, a single panel is cut in the form of a pair of abutting, congruent twelve-sided polygons that share a common uncut side, i.e., a single, dual-lobed panel, in which each lobe resembles an twelve-sided polygon having eleven cut edges. This single piece panel is then folded about an axis that coincides with the shared uncut side to allow the lobes to be superimposed in congruent fashion. By joining the respective eleven coincident cut edges, a polygonal cushion similar to the two-panel cushion of the first embodiment may be formed, but without the need for a joining operation along the shared side due to the lack of any cut edge.
The polygon shapes can be placed in close proximity to one another on the fabric blank from which they are cut, thus minimizing fabric waste and cost, and providing a useful advancement over the present art. In one embodiment, regular dodecagons are placed in such fashion that the number of sides of any given dodecagon that are coincident with adjacent dodecagons is in the range of two to six, depending on the position of the first dodecagon on the fabric blank. The fabric between polygon-shaped panels (the inter-panel fabric) tends to be in the shape of a triangle, having substantially straight sides, and is therefore easier to utilize in the manufacture of other air bag components (e.g., reinforcements or other components). In a second preferred embodiment, Alternating Side Length (ASL) dodecagons are placed in contiguous relation to one another, such that the number of sides of any given first dodecagon that are coincident with adjacent dodecagons is in the range of two to six, depending on the position of the first dodecagon on the fabric blank. In this embodiment, the inter-panel fabric is also generally triangular in nature due to the coincident sides of the ASL dodecagons, although the triangular inter-panel fabric is smaller than that generated by the regular dodecagons discussed above.
The advantages of the present invention, in all embodiments, include better fabric utilization and an overall simplification of the manufacturing process. By providing congruent polygonal fabric panels having linear edge segments, this invention facilitates seaming operations by improving the ease, effectiveness, and efficiency with which the cut pieces can be aligned and joined during the seam formation process. Prior designs tend either to result in relatively poor material utilization due to the use of unusual panel shapes or to require more complex aligning, folding or sewing operations during the seaming process than is found in the instant invention. The symmetry of the dodecagon-shaped panels makes folding operations simpler than in those air bags in which asymmetrical patterns are used. Accordingly, cost is lowered due to the improved yield per fabric blank as well as the increased efficiency with which the cutting and joining operations can be performed.
All of these advantages apply to the embodiment using two separate twelve-sided congruent polygon panels as well as to the embodiment using a single, dual-lobed panel, with congruent lobes in the shape of the same twelve-sided polygon. However, an additional advantage of the latter embodiment of this invention is the additional simplification in cutting and sewing operations this embodiment provides. Because of the common uncut boundary shared by the twelve-sided polygons comprising the lobes, the number of coincident panel sides or edges requiring joining (after the panel is folded and the lobes are superimposed in congruent fashion) generally is equal to eleven. Sewing along the entire length of the perimeter of the finished air bag is not required due to the presence of an intact section of fabric that forms an uncut transition between the respective lobes that become the face and rear panels of the air bag. The panel is folded along an axis coinciding with the common uncut side between the two polygonal lobes and the two lobes are superimposed in congruent fashion. This folding operation causes the respective cut edges of each lobe to coincide, thereby forming a layered, twelve-sided polygon having only eleven cut sides. Sewing is required on only the eleven cut sides of the folded panel. Each reduction in the number of sewn seams reduces the opportunity for rupture along a seam area, and reduces the number of necessary manufacturing steps. Accordingly, this invention, in each of its embodiments, is believed to represent a useful advancement over the present art.
The present invention relates to an air bag suitable for use in a vehicle occupant restraint system, wherein the panels that comprise the air bag are in the shape of a twelve-sided polygon. The panels may be cut separately from a fabric blank, or positioned in such fashion that the panels share a common side and create a dual-lobed figure. The use of dodecagon-shaped panels improves fabric utilization and fabrication efficiency, as compared with conventional circular panels.
In view of the foregoing, it is an object of this invention to provide an air bag that can be formed from fabric panels that are cut from a fabric blank with a minimum amount of wasted fabric. The blank may be of woven or non-woven fabrics, films, or combinations or composites thereof, as may be prescribed by those skilled in the art.
It is another object of this invention to provide a vehicle occupant restraint cushion or air bag that can be formed from two twelve-sided polygonal panels, or from a single panel comprised of two abutting polygonal lobes, without the need for any additional attachments, shape-forming members, or reinforcements to define the surface of the air bag.
It is yet another object of this invention to provide an inflatable restraint cushion that, in one embodiment, is comprised of two congruent polygon-shaped fabric panels in the shape of a dodecagon, where the number of sides in each panel is twelve. The panels are superimposed and aligned in congruent fashion to make the twelve edges coincident. The edges are then joined along their respective twelve cut sides by a perimeter seam comprised of a series of easily sewn, substantially straight seams. There is no need to fold either of the panels prior to the formation of the perimeter seam, and no need to orient the perimeter seam with respect to any fold line that may be used to facilitate storage of the uninflated air bag in an operative position within the vehicle.
It is yet another object of this invention to provide an inflatable restraint cushion that, in a separate embodiment, is comprised of two congruent polygonal-shaped fabric panels in the shape of an Alternating Side Length dodecagon, where the ratio of the length of the short sides to the length of the long sides is approximately one to two. The panels are superimposed and aligned in congruent fashion to make the twelve sides coincident. The edge portions are then joined along their respective twelve cut sides by a perimeter seam comprised of a series of easily sewn, substantially straight seams. There is no need to fold either of the panels prior to the formation of the perimeter seam and no need to orient the perimeter seam with respect to any fold line that may be used to facilitate storage of the uninflated air bag in an operative position within the vehicle.
It is still another object of this invention to provide an inflatable restraint cushion that, in another embodiment, is comprised of a single panel of fabric comprised of two congruent polygonal lobes that share a common uncut side. The two polygonal lobes are each in the shape of either a regular dodecagon or an Alternating Side Length dodecagon, where the number of sides in each lobe is twelve, but where each lobe has eleven cut sides. During assembly of the air bag, the two lobes are folded along an axis coinciding with the uncut twelfth side shared by the two polygons, and superimposed to form a flat, layered, polygonal structure with an aligned, congruent perimeter comprised of twelve straight sides, of which eleven are comprised of coincident cut edges. The folded polygonal structure is seamed or otherwise joined together along the eleven cut sides by sewing or other suitable techniques. Because the shared side of the polygonal structure comprising the twelfth side is uncut fabric, seaming along this side may be regarded as optional. Although seaming operations usually use sewing, it is contemplated that if coated or other suitable fabrics are used, the coincident cut edges of the two lobes can be welded or otherwise secured together by techniques known to those skilled in the art.
Applicable to each embodiment described above, it is contemplated that additional layers of fabric or other materials may be interposed or placed alongside one or both of the layers, either fully or partially, as the specific design may dictate. Upon appropriate inflation, the resulting flat cavity will form a restraint cushion or air bag that, when incorporated into an appropriate air bag system, is suitable for protecting the occupants of a vehicle involved in a collision.
In accordance with one aspect of the present invention, a method for forming the inflatable cushion of the present invention from two separate polygon-shaped panels is provided. This method comprises the steps of: (a) cutting from a fabric blank a first fabric panel in the shape of a regular or Alternating Side Length dodecagon; (b) cutting from a fabric blank a second fabric panel in the shape of a dodecagon that is congruent to the first fabric panel; (c) superimposing the first and second panels in congruent fashion, thereby forming a twelve-sided, layered polygonal structure in which the respective cut sides of each polygon are coincident; and (d) joining or sealing together along each of the coincident cut sides of the polygonal structure.
In accordance with another aspect of the present invention, a method for forming the inflatable cushion of the present invention from a single panel is provided. This method comprises the steps of: (a) cutting from a fabric blank a single panel having a dual-lobed shape comprised of a pair of congruent, twelve-sided polygons that share a common uncut side, each lobe thereby having the shape of a dodecagon having eleven cut sides and a twelfth uncut side along which it is seamlessly joined to the other lobe; (b) folding this dual-lobed panel along an axis that coincides with the uncut twelfth side shared by the pair of dodecagons, thereby aligning each of the eleven cut sides of each lobe with the corresponding cut side of the other lobe to form a perimeter substantially comprised of a layered polygonal structure in which the two lobes are superimposed in congruent fashion; and (c) joining or sealing together along each of the coincident cut sides of the polygonal structure.
Both the cutting and sealing operations may be achieved by manual, automated, or any other methods known by those skilled in the art. As is conventionally done, suitable holes may be cut in the rear panel or lobe to form gas inlet means, gas ventilation means, or for other purposes. It should be noted that various other structural devices or reinforcements may be incorporated into the design of the air bag which may result in the resulting polygonal structure or cushion having more than two layers.